Apparatus for establishing and maintain a constant-pressure environment

ABSTRACT

The invention comprises an apparatus for establishing and maintaining a constant-pressure environment and which permits the overall pressure within an enclosure to be changed by a single manipulation, said device comprising an enclosure, means for regulating the flow of a gas into the enclosure, means for regulating the flow of gas out of the enclosure, a gas source, a vacuum source, and means which (a) sense the pressure differential between the interior of the enclosure and the vacuum source, and (b) which activate the inlet and outlet means when this differential falls below or above a preselected value.

United States Patent {72] Inventors Robert S. Olson 3,415,582 12/1968 Trexler 312/1 Lalayette; 3,492,987 2/1970 Parker..... 312/1 Joseph P. Surls, Jr., Walnut Creek; David 2,652,847 9/1953 Segeharth 137/103 L. Bauer, Concord, Calif- 2,799,288 7/1957 Knight 137/98 [21] Appl. No. 766,110 2,883,998 4/1959 Broughton... 137/1 16.3 [22] Filed Oct 9,1968 3,048,185 8/1962 Howard 137/103 [45] Paten J n 3,1 3,111,957 11/1963 Broughton 137/116.3 [73] Assignee The D h mi l C mpany 3,228,702 1 1966 Ulm 137/251X Mldland Primary Examiner-Harold W. Weakley Attorney-Griswold and Burdick, C. E. Rehberg and .1. R. 54 APPARATUS FOR ESTABLlSHING AND Lochhead MAINTAININS? CONSTANT-PRESSURE ENVIRONME 1 Claim 3 Drawing Figs ABST RA CT. The invention comprises an apparatus for establishing and maintaining a constant-pressure environment [52] [1.5. CI and which permits the overall pressure with an enclosure to be 137/103, 137/251 changed by a single manipulation, said device comprising an [5 ll.-

enclosure means for regulating the flow of a gas into the en- Fleld of Search lo ure means for regulating the flow of gas out of [he enclo- 103,116.31, 11 312/1; 123/1-02 sure, a gas source, a vacuum source, and means which (a) 56 R f d sense the pressure differential between the interior of the en- I e closure and the vacuum source, and (b) which activate the UNITED STATES PATENTS inlet and outlet means when this differential falls below or 2,862,307 12/ 1 958 Bloomer 312/] above a preselected value.

Vacuum 1 50 area 1 20 Z 28 3 6 a 5 V 50 U ce APPARATUS FOR ESTABLISHING AND MAINTAINING A CONSTANT-PRESSURE ENVIRONMENT BACKGROUND OF THE INVENTION It is often desirable to regulate the operating pressure within an enclosure. One such enclosure is typically called a glove box" because it has one or more pairs of gloves connected to it in such a way that a worker can place his hands therein and work inside the enclosure without exposing his skin to the enclosure '5 interior environment. Another advantage of such regulation is the ability to choose the components of the environment, e.g., oxygen can be excluded if desired.

It is desirable that the pressure within a glove box" be kept reasonably close to atmospheric pressure in order that the operator does not become fatigued. To accomplish this requires that gas be discharged from the enclosure when its interior volume is decreased by inward movement of the hands in the gloves, and that gas be added to the enclosure when the volume is increased by outward movement of the gloves.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, briefly, is a schematic drawing of the invention in its broadest scope.

FIG. 2 shows one possible arrangement of the major components of such a device, and their individual parts.

FIG. 3 shows a preferred embodiment of the invention.

DESCRIPTION OF THE INVENTION More precisely, FIG. 1 embodies the invention in its broadest scope, i.e., an apparatus for establishing and maintaining a constant-pressure environment, which comprises:

A. An enclosure 30;

B. Means 6 for (a) sensing the pressure differential between the interior of the enclosure 30 and a vacuum source 50, and (b) regulating the flow of gas from a source into the enclosure when said differential falls below a predetermined value;

C. Means 8 for (a) sensing the pressure differential between the interior of the enclosure 30 and the vacuum source 50, and (b) regulating the flow of gas out of the enclosure when said differential rises above a predetermined value;

D. Conduits 26 and 32 connecting means 6 and 8 respectively to the enclosure 30;

E. Conduits I2 and 36 connecting means 6 and 8 to the gas source 10 and the vacuum source 50 respectively;

F. Conduits 28 and 48 connecting means 6 and 8 respectively to the vacuum source 50.

Any enclosure in which it is desirable to maintain a constant, or near constant, pressure forms a suitable part of the apparatus of this invention. The preferred enclosure is of the type designated as a glove box," as described above.

The gas source can suitably be any source of gas under a pressure greater than the pressure to be maintained in the enclosure. A cylinder of compressed gas is, for example, suitable.

The vacuum source suitable is any device capable of producing a steady pressure somewhat less than the pressure desired in the box. This device serves two functions: (a) to produce a reference pressure for the inlet 6 and outlet 8 pressure differential sensing means, and (b) to provide a low-pressure sink" for gases exhausted by the outlet means 8.

Any vacuum pump is suitable for the above, but a centrifugal blower is preferred because of its constant-pressure characteristic when gas flow is varied, and the ease of varying the speed of said blower, thus varying the vacuum produced.

An array of devices are suitable for performing the dual functions of means 6 and 8, i.e., to sense the pressure differential, and to regulate gas flow accordingly. These devices will be discussed in the description of FIGS. 2 and 3 below.

Generally the device functions as follows. For convenience sake, the practice of the invention will be typified by a glove box" as the enclosure. Pressure will be absolute, assuming atmospheric pressure: 760 mm. Hg.

Typically a glove box should be operated within approximately 8 mm. Hg of atmospheric pressure (P,,) in order to assure the comfort of the operator and ease of glove manipulation. Therefore, the boxs pressure should fall within the range of752 mm.768 mm. Hg.

Generally a variance of 1 mm. Hg within the box will not disrupt operations. Such a variance will allow the box to be operated without a constant flow of gas, which would be the case if no variance was established. Therefore, small box volume changes will not generally require pressure regulation.

The pressure within the box (P is selected, preferably within the above-described range (for example, 765 mm. Hg), and can be allowed to vary within 1 mm. Hg, i.e., 764.5 to 765.5 mm. Hg.

The vacuum source is then adjusted to produce a pressure, P below P and preferably only slightly below P,,, but in any case below atmospheric pressure. Suitably, the differential between P, and P should be of the order of5-50 mm.

Since the regulators 6 and 8 on the inlet and exit lines of the box use P as their reference pressure, they are now set to open at pressures slightly (e.g., 0.5 mm.) below and above P respectively. The box is then ready for use.

Having once set the regulators 6 and 8 to operate at a fixed differential above P,, their operation is then independent of the chosen value of P,,, the latter depending only on the chosen value of P Hence, the operating pressure P, can be changed at will by merely adjusting the vacuum source to produce the appropriate value of P' The value of P will be a linear function of P Accordingly, any desired new value of P is attained by merely adjusting the vacuum source to establish the appropriate value P without making any adjustment of the inlet and outlet mechanisms and controls 6 and 7.

If the chosen P is 765 mm., the vacuum source, such as a pump, might be set to produce a pressure, P,,,, between, for example, 700 and 755 mm. Having arbitrarily chosen, say, 750 mm., means 6 is then adjusted to open the inlet valve when P is less than 14.5 mm. above P i.e., less than 764.5 mm. Likewise, means 8 is adjusted to open the exit valve when P is more than 15.5 mm. above P,,,, i.e., more than 765.5 mm. Each valve, of course, is adjusted to close when it has effected a pressure correction of the order of 0.5 mm. The box is now ready for use at a pressure of 765i0.5 mm. Should it now be desired to change P to a new value, say 756 mm., a decrease of 9 mm., it can be done by merely adjusting P to a value 9 mm. lower, i.e., to 741 mm.

The precise manner of setting means 6 and 8 depends upon the type of equipment used, and will be illustrated in the discussion of FIGS. 2 and 3.

FIG. 2 illustrates one possible arrangement of components to accomplish pressure regulation in an enclosure. It comprises:

A. An enclosure 30;

B. Sensing means 22 and 40 for sensing the pressure differential between (a) the interior of the enclosure 30, connected thereto by conduits 24 and 38, and (b) a vacuum source 50, connected thereto by conduits 28 and 48, said means adapted to developing a signal of at least a certain magnitude when the pressure differential is below or above, respectively, a preselected value;

C. Valve actuator 18 and valve 14 for regulating the flow of gas into the enclosure 30, connected to a source of gas 10 by a conduit 12 and to the enclosure by a conduit 26, and adapted to admit gas to the enclosure in response to a signal from the sensing means 22 in excess of the set point" of actuator 18, i.e., when the pressure differential falls below a preselected value;

D. Valve actuator 44 and valve 34 for regulating the flow of gas out of the enclosure 30, connected to the vacuum source 50 by a conduit 36 and to the enclosure by a conduit 32, and adapted to permit escape of gas from the enclosure in response to a signal from the sensing means 40 in excess of the set point" of actuator 44, i.e., when the pressure differential rises above a preselected value;

E. Signal-transmitting means (16, 20, 42 and 46) connect- 7 ing valve actuator means 18 and 44 to sensing means 22 and 40 and valves 14 and 34. v

Essentially, the device represented by FIG. 2 is identical to that of FIG. 1, except that means 6 and 8 are detailed.

Means 22 and 40 receive pressures from the enclosure and the vacuum source. The differential therein is then transmitted to valve actuators 26 and 44, said actuators operating the inlet valve 14 or outlet valve 34 when the conditions noted above arise. It is; thus apparent that one pressure-sensing means could suffice; two are shown merely for clarity of illustration.

Various devices can be utilized for the sensing means and actuating means. For instance, a diaphragm pressure sensor is suitable. An electrical device responsive to the signal from the sensor, such as a solenoid in the plate circuit of a gas-fired triode biased by the signal, makes a suitable valve actuator. It is also possible to combine the sensor and actuator into one device as, for instance, a mercury U-tube with electrical contacts. Other suitable'devices are well known in the process control instrument art.

The manner of setting the inlet and outlet means to admit or exhaust gas depends upon the equipment used, as noted above.

If a diaphragm pressure sensor is used which develops an electrical signal-directly proportional to the magnitude of the measured differential, the signal can be transmitted to a valve actuator, comprising, for instance, an electrical circuit comprising a variable resistor. A resistance, then, corresponding to a certain pressure set point" can be selected.

In the case ofa mercury U-tube, by changing the amount of mercury and the distance between contacts, the valve can be set to open or close at any desired pressure differential.

FIG. 3 shows a preferred embodiment of the apparatus of this invention. It differs from the device of FIG. 2 only in the outlet means, which, in this embodiment, comprises a sealable container 54 connected to:

A. The enclosure 30 by a conduit 52, said conduit ter minated near the bottom of the container 54, and sealed within the container;

B. The vacuum source 50 by a conduit 58, said conduit sealed to the container at its point of exit therefrom, said container containing a suitable fluid 56.

The device of FIG. 3 differs from that of FIG. 2 in that a bubbler pressure-relief valve is the outlet valve, actuator and sensing means. The use of a bubbler has the advantages over other types of controls of simplicity and ease of adjustment.

The operation of the total system is unchanged except that the pressure differential at which gas will exhaust from the bubbler is determined by the depth of immersion of conduit 52 in the liquid 56 contained in the container 54.

Water is a suitable fluid for use therein. Also inert hydrocarbons with low vapor pressure-densities are also suitable, e.g., mineral oil and silicone oils.

We claim:

ll. An apparatus comprising:

A. A generally gastight glove box enclosure including one or more gloves;

B. A source of gas of the same type as that to be utilized in said enclosure, said source being at a pressure above the operating pressure of said enclosure;

0. Means for admitting gas from said source to said enclosure when the pressure differential between the interior of said enclosure and a centrifugal blower vacuum source falls below a predetermined level;

D. Means for sensing said pressure differential between the interior of said enclosure and the blower; and

E. A centrifugal blower vacuum source, said blower producing a pressure essentially constant when gas flow through the blower is varied, said blower being in communication with the enclosure through a bubbler pressure-relief valve, said bubbler acting as both a means for sensing the pressure differential between the interior of the enclosure and the blower, and as a means for exhausting gas from said enclosure to said blower when the pressure differential rises above a predetermined value; whereby, as said pressure differential tends to change, the gas-admitting means or bubbler, respectively, admits or exhausts gas so as to maintain an operating pressure within said enclosure within a predetermined range. 

1. An apparatus comprising: A. A generally gastight glove box enclosure including one or more gloves; B. A source of gas of the same type as that to be utilized in said enclosure, said source being at a pressure above the operating pressure of said enclosure; C. Means for admitting gas from said source to said enclosure when the pressure differential between the interior of said enclosure and a centrifugal blower vacuum source falls below a predetermined level; D. Means for sensing said pressure differential between the interior of said enclosure and the blower; and E. A centrifugal blower vacuum source, said blower producing a pressure essentially constant when gas flow through the blower is varied, said blower being in communication with the enclosure through a bubbler pressure-relief valve, said bubbler acting as both a means for sensing the pressure differential between the interior of the enclosure and the blower, and as a means for exhausting gas from said enclosure to said blower when the pressure differential rises above a predetermined value; whereby, as said pressure differential tends to change, the gas-admitting means or bubbler, respectively, admits or exhausts gas so as to maintain an operating pressure within said enclosure within a predetermined range. 